JPS5858438B2 - Cobalt-tin alloy plating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cobalt-tin alloy plating bath.

A fluoride bath using acidic fluoride is known as a practical method for forming a plating film on a cobalt-tin alloy.
Also, as a brightening agent, titanium is used as a fluoride complex ion (TiF).
Baths with additives in the form of 4"-") are also well known.

However, these fluoride baths are accompanied by severe corrosion;
It is difficult to maintain the equipment, etc., and it is also difficult to treat drainage and exhaust gas, and its use is not desirable from the standpoint of pollution control and occupational health.

In contrast, a plating method has been attempted in which a coating of cobalt-tin alloy is formed using a pyrophosphoric acid bath.

However, this method also yields only a gray or off-white plating film, giving unsatisfactory results.

In addition, 50 to 120 ml of concentrated ammonia water is added to 10,100 O of a plating bath whose main component is an alkali salt of cobalt salt-stannic salt pyrophosphoric acid, and additives such as amines, proteins, and amino acids are added. It is also well known to add mercapkuns alone or in combination; however, even with this method, the pH changes rapidly and streaks are generated in areas of high current density, often resulting in defective plating.

The object of the present invention is to obtain a stable and beautiful coating of cobalt tin alloy without using fluoride and without forming streaks even in high current density areas.

The bright cobalt-tin alloy electroplating bath of the present invention contains 2 to 10 g/l of cobalt salt as Co and 1 as Sn.
0-409/l stannous salt and 150-2009/1
20 to 120 g/l of one or more inositol phosphate esters and/or their salts and 5 to 20 g/l of one or more acetylene alcohols to an electroplating bath containing pyrophosphate as a main component. It is characterized by adding g/l.

The inositol phosphates and their salts to be added to the present invention are inositol phosphates, alkali metal salts of inositol phosphates, alkaline earth metal salts of inositol phosphates, and ammonium salts of inositol phosphates, and their use. The amount is 20g~1
2Of! /13.

In addition, the acetylene alcohol added to the present invention is one that does not have a triple bond at the end of the molecule, such as 2-butyne-1,4-diol, pentylene-diol, hexyne-diol, etc., and the amount used is 5 to 209%. It is 11.

In a bath consisting of a cobalt salt, a stannous salt, and potassium pyrophosphate, cobalt pyrophosphate is relatively poorly soluble in an aqueous solution of potassium pyrophosphate, and the ratio of cobalt as a metal to potassium pyrophosphate is 1:15 parts by weight or more. Otherwise, if left for a while, precipitation will occur resulting in a defective plating bath.

However, if inositol phosphate esters or salts thereof are added individually or in combination, no precipitation will occur even if the ratio is less than 1:15 parts by weight, and a defective plating bath will not result.

Because of its excellent chelate-forming ability, it can be used in an extremely stable cobalt-tin alloy plating bath, and can be directly used in plating operations without performing dry electrolysis.

A beautiful white plating film without streaks can be obtained.

The metal salts used in the present invention include stannous salts such as stannous chloride, stannous sulfate, and stannous pyrophosphate;
Examples of cobalt salts include cobalt chloride, cobalt sulfate, cobalt acetate, and cobalt hydroxide.

10-40g of metal tin per liter of plating solution
, the amount of cobalt is 2 to 10 g, and the sum of the metal concentrations is preferably 50 g or less.

If the concentration is higher than this, a large amount of solvent will be consumed and the concentration of the plating solution will become high, which is not preferable.

The concentration of pyrophosphate in the electroplating bath of the present invention is 1
It is 50-200 g/11.

One or more compounds selected from the group consisting of inositol phosphate esters and their salts used in the present invention (20 to 120 g per liter of plating solution).

It is also necessary to maintain the amount twice the molar concentration of the sum of all metal concentrations as the minimum limit.

The plating solution of the present invention has a pH of 8.0 to 9.0, a temperature of 40 to 50°C, and a current density of 0.1 to 3.0 A/dm.

Mechanical stirring and cathode rocker are effective at this time, but
Satisfactory results can be obtained even when electrodeposition is performed in a stationary state.

The liquid also has excellent flexibility, for example, when the inner diameter is 61nrIL1
When a 300 mm long iron pipe was plated with a current of IA for 1 minute, the inside as well as the outside was completely coated with the alloy coating, and the strength and strength were sufficiently satisfactory.

Furthermore, this test piece complies with JIS H8612 and JISH86.
Pinhole test according to 13 standards, 150℃ for 30 minutes,
Changes in the state of the plated surface were observed through a heat cycle test at room temperature for 30 minutes, and satisfactory results were obtained.

The appearance of the bright tin-cobalt alloy coating obtained from the alloy plating solution of the present invention is very similar to that of chrome plating, and the corrosion resistance is also dissimilar.

If an amino acid such as cystine is further added to the alloy plating solution of the present invention, a film with a deep black color can be obtained.

The coating was subjected to a salt spray test according to the JIS Z2701 method, but there was no change even after 6 cycles.
No discoloration even if left for 0 to 40 days, 0.4-1. Even when the Cron film was immersed in concentrated nitric acid (36N) for 1 minute, no trace of corrosion was observed, and furthermore, there was no discoloration or corrosion from the fingerprint area, and no changes were observed.

The adhesion of the alloy coating is also excellent. For example, the alloy plating coating of the present invention can be electrodeposited on materials plated with iron, silver, copper, and iron-copper-nickel, and the alloy coating according to the present invention can be electroplated to meet JISH867.
A bending test was conducted using method 2, but no peeling occurred.

Furthermore, a Cellotape test using a 1 mm grid grid was also conducted, but no peeling occurred.

Next, the present invention will be explained by examples.

In this case, the conditions and abbreviations of the basic bath to be tested are as follows.

(1) e.

1 acid power 150-2009/l 180 g/l Lium(2) Stannous chloride 15-25 g/ 120 g/
1(3) Cobalt chloride 8-15g/l 10g/
1 (4) pH 8-98.5 (5) Temp %℃ 40-5045 (6) Cathode current density (D2) 2VD2 (7) Anode carbon plate (8)
) Stirring Mechanical stirring (9) Cathode
Shinchu plate compound with bright nickel plating Abbreviation (a) Inositol phosphate ester Ph (b) Ammonium salt of inositol phosphate ester Ph-NH4 (c)
Sodium salt of inositol phosphate Ph-Na Example 1 50g of Ph-(NH4)6/10g of CBu in basic bath
/l was added and plating was performed to obtain a beautiful silvery-white chrome electrodeposit.

Example 2 Add P h 209/l to the basic bath and adjust the pH to 8 with NaOH.
5, and then plating was performed by adding 15 g/l of Bu, and the same satisfactory results as in Example 1 were obtained.

Example 3 P h 20 g/l was added to the basic bath, the pH was adjusted to 8.5 with KOH, and then 10 g/l of Pe was added and plating was performed, obtaining the same results as in Example 1. .

Example 4 Ph and Ph-NH4 were added at 15 g/l each and Bu at 10 g/13 to the basic bath, and plating was carried out to obtain satisfactory results in the same manner as in Example 1.

Example 5 209/11 and 30g of Ph and Ph-Na in the basic bath, respectively
The same results as in Example 1 were obtained by adding 59/l of /11Pe and performing plating.

Example 6 Ph-NH415i/l, Ph-Mg 1 in basic bath
Plating was performed by adding 0 g/l and He 7 g/l, and the same results as in Example 1 were obtained.

Example 7 20g/l of Ph-Ca, 5g/l of Bu and Pe in the basic bath
Plating was performed by adding 2.5 g/l, and the same results as in Example 1 were obtained.

Example 8 Ph 7 g/l, Ph-NH415 g/l in basic bath
l.

Pe39/1SHe 2g/1. Add and perform plating,
The same results as in Example 1 were obtained.

Example 9 An experiment was conducted by changing the types and amounts of inositol phosphates and acetylene alcohols as shown in Tables 1 to 5.

The results are shown in Tables 1 to 5.

Those that obtained satisfactory results similar to those in Example 1 are marked with an ○ mark, the occurrence of streaks and partial brutality are marked with a △ mark, and the electrodeposited surfaces are not alloyed and are poorly plated with tin or cobalt alone, marked with an × mark. and show the results.

If the amount of inositol phosphate ester is extremely small, cobalt will precipitate and the plating solution will become cloudy, and the floating matter will make the coating surface cloudy and cause poor plating.

This is indicated by ■ in Groups 1 to Table 5.

Furthermore, if the amount of inositol phosphate ester is small, tin precipitation will increase, and the corrosion resistance of the alloy coating will be significantly impaired.

The effects are summarized in Table 6.

The surface area of the test piece was 1 dm2, the temperature was 20° C., and the weight loss after 1 minute of immersion showed corrosion.

Like chromium, it showed no corrosion resistance to hydrochloric acid.

Claims (1)

[Claims] 2-10 g/l cobalt salt as ICo, 10-40 g/l stannous salt as Sn, and 150-2
00 g/! 20 to 120 g/l of one or more inositol phosphate esters and/or salts thereof to an electroplating bath containing pyrophosphate as a main component.
and one or more types of acetylene alcohols, 5 to 20 g/
A bright cobalt-tin alloy electroplating bath characterized by the addition of l.